20728123 has 4 divisors (see below), whose sum is σ = 22322608. Its totient is φ = 19133640.

The previous prime is 20728121. The next prime is 20728133. The reversal of 20728123 is 32182702.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 20728123 - 2¹ = 20728121 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20728121) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 797223 + ... + 797248.

It is an arithmetic number, because the mean of its divisors is an integer number (5580652).

Almost surely, 2^20728123 is an apocalyptic number.

20728123 is a deficient number, since it is larger than the sum of its proper divisors (1594485).

20728123 is a wasteful number, since it uses less digits than its factorization.

20728123 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1594484.

The product of its (nonzero) digits is 1344, while the sum is 25.

The square root of 20728123 is about 4552.8148435885. The cubic root of 20728123 is about 274.6966263298.

The spelling of 20728123 in words is "twenty million, seven hundred twenty-eight thousand, one hundred twenty-three".